1. Field of the Invention
This invention relates to a fine positioning device and is more particularly concerned with such a device useful, for example, as a stage positioning device in a scanning tunneling microscope by which the shape of the surface of a substance, the very minute texture of the substance and the surface property of the substance may be observed in a non-contact fashion and with a high resolving power.
2. Related Background Art
A scanning tunneling microscope of this kind is known from U.S. Pat. No. 4,343,993. A probe used to detect a tunnel current by the scanning tunneling microscope is fixed to a base bed through an actuator constituted by piezo-electric elements which act in the directions of the x-axis, the y-axis and the z-axis, respectively. The piezo-electric elements acting in the directions of the x-axis and the y-axis are driven to displace the probe so as to scan a measurement sample, and the piezo-electric element acting in the direction of the z-axis is driven to control the distance between the sample and the probe.
In the above-described example of the prior art, the scanning range of the probe is limited to the stroke per se of the piezo electric elements As a method of solving this problem, it is conceivable to make the stroke of the piezo-electric elements great, but the resulting strains in the piezo-electric elements would introduce error in the position of the probe relative to the voltage applied to the piezo-electric elements.